Work hours?

I am just starting to explore the power of PostgreSQL's time and date
functionality. I must say they seem very powerful.

I need to write a function that, given a month, and a year as input returns
the "work hours" in that month. In other words something like

8 * the count of all days in the range Monday to Friday) within that
calendar month.

Any thoughts as to the best way to approach this?


-- 
"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                        -- Benjamin Franklin